|   | 
				
					
	
		  | 
	 
	
		| Paper: | 
		On the Primordial Helium Abundance and the ΔY/ΔO Ratio | 
	 
	
		| Volume: | 
		374, From Stars to Galaxies: Building the Pieces to Build Up the Universe | 
	 
	
		| Page: | 
		81 | 
	 
	
		| Authors: | 
		Peimbert, M.; Luridiana, V.; Peimbert, A.; Carigi, L. | 
	 
	
	
		| Abstract: | 
		We present a review on the determination of the primordial helium abundance, Yp, based on the study of hydrogen and helium recombination lines in extragalactic H ii regions. We also discuss the observational determinations of the increase of helium to the increase of oxygen by mass ΔY/ΔO, and compare them with predictions based on models of galactic chemical evolution. | 
	 
	
		| 
			
			
		 | 
	 
	
		  | 
	 
 
					 
				 | 
				  |